The invention relates to a method and a device for guiding the movement of a moveable machine element of a machine.
In order to guide the movement of a moveable machine element of a machine such as, for example, a machine tool, production machine and/or a robot, the generation of desired reference variables such as for example, desired position, desired speed and/or desired acceleration, as desired control variables for the controls connected to a controller, for controlling the motors of the machine that provide the drive for the travel movement of the machine element is one of the central tasks of the controller. Each machine in this case generally has a number of machine axes, it being possible for each machine axis to move in a direction of the machine axis, generally with the aid of a motor assigned to said machine axis and further components, such as for example a gearbox of the moveable machine element, it being possible for the machine element to be present, for example, as a tool slide with a clamped workpiece and/or, for example, in the form of a tool. The motor, the further components and the machine element in this case constitute elements participating in the movement.
When calculating the desired reference variables for the individual machine axes of a machine, modern controllers mostly take account of the efficiency of the relevant machine axes in such a way that the reference variables are generated in such a way that the permissible limiting values are not exceeded during the movement of the moveable machine element. In order, moreover, to avoid exciting critical natural frequencies of the elements participating in the movement, it is customary in the art to carry out various measures that are, however, attended by in part considerable losses in the dynamics of the movement operation of the moveable machine element. One of these measures is, for example, the so-called jerk limitation. The change in the acceleration, that is to say the jerk, is prescribed in accordance with specific profiles or is held within defined bounds. Particularly in the case of machine tools, the path speed of the movement to be carried out is reduced until the jerk limitations of the individual machine axes are complied with and the path jerk defined on the path is not exceeded. It follows that a targeted adaptation to the vibration behavior is possible only to a very limited extent, particularly in the case of machine tool applications. The jerk must be greatly reduced in the interests of an adequate accuracy of fabrication, and so the dynamics are substantially restricted, and this leads to higher fabrication costs.
A further known possibility is the use of so-called cam disks. In many applications, particularly as production machines, the individual values of the desired reference variables are generated with the aid of cam disks. The cam disk profiles are composed in this case from polynomials. The aim 1n this case is to achieve a low vibration excitation by means, for example, of heuristic stipulation (cam disks as “soft” as possible, use of polynomials of high order). An adaptation to the mechanical vibration behavior of the elements participating in the movement can be attended by a corresponding slowing down of the process, something which is likewise already accompanied by the above-named disadvantages.
A further known possibility for reducing the vibration load is so-called linear desired reference variable filters. In this case, linear filters are used to reduce the spectral components in the range of critical frequencies. However, a signal delay is always associated with such filtering. Particularly in the case of machine tools, inaccuracies in fabrication therefore arise.